Filter frame



May 28, 1946. R. J. BRANDT FILTER FRAME Filed May 15 1944 I: rtlllllllllllfllllllt' INVENTOR. tZ'BeAA/O ATTORNEY.

Fatented May 28, 194

UNITED STATES PATENT OFFICE FILTER FRAME Robert J. Brandt, Los Angeles, Calif.

Application May 13, 1944, Serial No. 535,425

1 Claim.

The invention relates to a filter frame which may be employed to hold a filter element such as a colored sheet of gelatine or the like. Such filters are commonly used for photographic purposes, namely, in front of an are light employed to illuminate a motion picture set. Heretofore it has been proposed to make the filter frame of sheet metal by arranging two circular holes in the metal sheet which is bent so that the holes overlap, a filter element is inserted in the holder thus formed, and this holder is secured in a frame which is formed by bending a sheet metal strip around the edges of the holder. This has a number of disadvantages, as follows. In the first place, such filter frames are commonly employed in an elevated position above the motion picture set, the arc lights being arranged on and overhanging a'so-called parallel. The front of the searchlight is not readily accessible, and the operator has to hold on to a railing with one hand and, with a filter in the other hand, fish for the place in front of the are light where the filter is to be inserted. If the filter is accidentally dropped, this is apt to cause serious injury to the people on the stage below, as the sheet metal type of filter frame has rather sharp edges. Another disadvantage is that no convenient means are provided for substituting a new filter element if the old one becomes damaged. Another disadvantage is that under the heat of the are light. the filter shrinks, whereas when the sheet metal type of filter frame is put together the edges may be hammered down so tightly on the edge of the filter medium that its shrinkage is not possible and hence it either wrinkles or breaks.

The above defects are overcome according to the present invention by providing two filter frame members which are free from sharp edges and which may be readily assembled about a filter medium, removable means being provided to hold the frame elements together under tension to allow for shrinkage of the filter.

For further details of the invention reference may be made to the drawing wherein Fig. 1 is a plan view of a filter frame according to the present invention.

Figs. 2 and 4 are sectional views on lines 2-2 and 44, respectively. of Fig. 1.

Fig. 3 is a sectional view corresponding to Fig. 2 but with the filter frame elements overlapped to facilitate insertion and removal of the spring clips which hold the frame elements together.

Referring in detail to the drawing, the filter frame 1 comprises a pair of similar frame elements. one of which is shown at 2 in Fig. 1, and the other of which lies immediately below it, as seen in Fig. l, as will be apparent from Figs. 2 and 4.

The element I comprises a plurality of coaxial and coplanar rings which may be of metal, and

of which three, namely numbers 3, 4 and 5 are shown in Fig. 1. The rings 3, 4 and 5 are crossconnected by tie rods such as 6 and 1 arranged at spaced intervals and welded or otherwise fastened to the rings. The lower frame element 2' has three rings similar to 3, 4 and 5 as indicated at 8, 9 and ii] in Figs. 2 and 4. The rings 8, 9 and ID are likewise tied together by tie rods indicated at dotted lines II and i2, etc.

A sheet I3 of the filter medium is arranged between the frame member 2 and the similar frame member 2' made up of the rings 8, 9 and In, the frame members 2 and 2 of course extending around the periphery of the filter l3.

The frame members 2' and 2' are held in superposed relation with the filter i3 therebetween by means of a plurality of spaced spring clips 14 which are substantially U-shaped with the outer rings such as 3 and 8 resting in the bight of the U, and with the legs l5 and it having transversely curved portions l1 and I8, respectively, to fit over the inner rings such as 9 and 4.

When it is desired to take filter frame i apart, the frame members 2 and 2' have enough flexibility so that a portion of the rings 3, 4 and 5 may be overlapped with the corresponding rings 8, 9 and Ill, as shown in Fig. 3, to reduce the overall thickness of the filter frame I, to thereby facilitate insertion and removal of the spring metal clips l4.

The clips M are arranged at spaced intervals around the filter frame I as shown in Fig. 1 and they hold the frame members 2 and 2' together as a unit and also hold them together with tension, thereby permitting shrinkage of the filter l3 when it is heated. Also, this construction avoids the use of sharp edges and provides a filter frame which is comparatively light in weight and which can be readily put together or taken apart to insert or remove filter l3.

It will be apparent that various modifications may be made in the invention without departing from the spirit of the following claim.

I claim:

A filter frame comprising a pair of frame members each comprising inter-connected coaxial and inner and outer coplanar rings, spring clips constructed and arranged to embrace the edge of said frame members and having an interlocking connection with said inner rings for resiliently holding said frame members superposed as a unit, the rings of one frame member being of substantially the same diameter as the corresponding rings of the other frame member and being flexible to permit the corresponding rings of said frame members to be overlapped to decrease the overall thickness of said pair of frame members to facilitate insertion and removal of said clips,

ROBERT J. BRANDT. 

